1. Field of the Invention
This invention relates to monitoring current and voltage in branches of an ac electrical power distribution system, and more particularly to apparatus which can be locked to the conductors of the ac distribution system at any location along the conductors.
2. Background of Information
The above-referenced related applications and U.S. Pat. No. 5,315,531 disclose a system for monitoring the energy consumed at multiple locations below the electric meter which is typically installed by a utility on the main power lines serving a customer. This system allows the customer to determine consumption for each location below the meter and allocate costs accordingly, if desired.
The energy monitoring system includes a modular unit at each location to be monitored. Each modular unit has a toroidal coil inductively coupled to each phase conductor of the ac distribution system by passing the conductor through the coil. The coils are mounted in a housing having through passages extending through the toroidal coils so that the conductors pass completely through the housing. Stabs extending from the housing adjacent the through passages engage the terminals on a circuit breaker together with the ac conductors to provide a voltage pick-up for the unit and to secure the unit to the circuit breaker. Thus, these units are referred to as piggy back units since they are mounted to the circuit breaker.
The piggy back units include circuitry which digitizes the analog currents and voltages sensed by the toroidal coils and the stabs, respectively, and calculates power and energy consumed utilizing an on board microprocessor. The energy monitoring system also includes a central., personal computer (PC) which is linked to each of the piggy back units by a simple two-wire synchronous communication line daisy chained between the units and the PC. The PC gathers the calculations generated by each of the local units for use in allocating billing.
The piggy back units are dimensioned to match the dimensions of the circuit breaker and can be secured to the circuit breakers mounted in a load center without requiring modifications to either the circuit breaker or the load center. There is a need; however, to be able to tap the monitoring units into the power distribution system at locations other than at a conductor termination, as is currently required for the voltage stab.
There is a further need for a monitoring apparatus which can monitor the current and voltage at any point along the conductors of the power distribution system and which does not require stripping of the conductor for the voltage connection.
There is also a need for such a monitoring apparatus which can lock the monitoring unit simply to any location along the conductor.